I donīt know a game that has better balanced weapons in multiplayer than Quake3, and yes, I still play it every day. Every weapon has itīs special strengthīs and weaknesses, itīs balanced out almost perfect. The only un-balanced weapon is the BFG, but itīs just included in 3 maps! And you wonīt find it in most custom maps.
Quake3's weapon balance was horrible, weapons that were supposed to do lots of damage didn't, and the ones that were supposed to do alot fires way too quickly.
Gauntlet: if you can get cose enough it deals a very effective ammount of damage
Machinegun: start weapon, fairly weak, but instant hits, medium accuracy and high rate of fire ---> usefull both for short and long range combat, thatīs what a start weapon has to be!
Shotgun: most effective on short range, long reload time, inaccurate on long range, but still usefull because of isntant hit projectiles!
Grenade launcher: the only weapon which could be a bit better (Quake1 GL was better), because the grenades bounce too wildly, but it can be damn usefull in certain maps.
Rocketlauncher: high damage + splash damage, medium relaod time, slow moving projectile, high accuracy...you know it.
Plasma gun: medium damage + splash damage, high rate of fire, fast projectiles
Lighting gun: highest rate of fire, high damage, high accuracy (good aiming required), limited range.
Railgun: very high damage, highest accuracy, long relaod time.
Except the BFG, and the special role of Gauntlet and MG, there is no weapon superior to the other in every situation. Thatīs what I call balanced. The cobination of weapons makes the simple deathmatch more interesting introduces strategy. For example, use the railgun on long range, then quickly finish it with some machinegun bullets after a hit. Push someone into the air with rocketsplash, then catch him with the lightning, things like that.
Unreal Tournament for example, makes itīs weapons balanced by overpowering (almost) each of them...cheap.